This application relates to devices and techniques for optical signal processing.
Data communications and signal processing in the optical domain can be implemented to achieve various technical advantages, e.g., high-speed communication and processing with reduced electromagnetic interference, and parallel processing. All optical inverters and all optical flip-flop devices are building blocks for all optical processing devices and circuits and have attracted extensive research attentions since 1980's. For example, all optical inverters and all optical flip-flop devices can be used in a wide range of applications, including, among others, all-optical memory, optical 3R regeneration for signal reamplification, retiming and reshaping, and optical header computation. An all-optical inverter can be used as a building block to construct various other optical logic gates and signal processing devices, e.g., a nucleus of all-optical combinational as well as sequential digital logic circuits such as NAND gates, flip-flops, arithmetic logic units and microprocessors.
All optical logic devices can be built based on the optical bistability (OB) effect or cross gain modulation (XGM) in in-plane semiconductor optical amplifiers (SOAs) to demonstrate optical inversion. OB has been shown to require high set/reset powers. Because of the two terminal nature of the OB devices, such OB inverters were not cascadable and therefore had limited use. XGM has been more thoroughly investigated, primarily in SOAs using traveling wave structures in which an optical beam travels through a semiconductor gain medium with a single pass without being confined in the semiconductor gain medium by an optical cavity. Many SOAs in traveling wave structures exhibit high optical noise and consume greater than 100 mW per device. SOAs in traveling wave structures are edge emitting SOAs where light is directed into the SOA and exits SOA along a direction parallel to one or more active semiconductor gain layers and the underlying substrate. It can be difficult to use such SOAs to provide 2-D array integration capability and, as such, such edge emitting SOAs have limited use in optical devices and systems that require a large number of integrated components.